Since the first planets outside of our solar system were discovered in the early 1990’s, nearly 300 planets have been discovered. However, if you were hoping to relocate, think again; most of them are Jupiter or Saturn-like planets: big, hot, and navigating very close to their star.

But just last week astronomers using the HARPS instrument on the European Southern Observatory's 3.6-meter telescope at La Silla, Chile, discovered three super-Earths: planets larger than our own, but still small enough that they could be rocky.

"Being able to find three Earth-mass planets around a single star really makes the point that not only may many stars have one Earth, but they may very well have a couple of Earths," said Alan Boss, a planet formation theorist at the Carnegie Institution of Washington in Washington, D.C.

Two methods are used to detect planets out of our own solar system, and both are very fine edged. The first method, known as the radial velocity method, looks for slight wobbles in a star that could signify the pull of a large enough planet. The second, the transit method, looks for a diminishment of light from a far away star that suggests an object has traversed in front of it.

But both methods are troublesome, considering the relative size of planets compared to their parent stars. Planets large enough to create a wobble visible from Earth with our current level of technology are obviously far and few between. The same limiting technological advancement hinders our ability to detect every small waver in light making its way to Earth, signifying a planet moving in front of it.

But as the years go by, our technology continues to advance; it is this fact that excites astronomers, bringing us closer and closer to finding a twin-Earth.

"I think why astronomers are really excited is it just shows that technology has really matured and so they're able to see these very subtle wobbles due to these low-mass planets," said David Charbonneau of the Harvard-Smithsonian Center for Astrophysics in Massachusetts, regarding the discovery of the three super-Earths. "Those were fairly massive stars. If they were able to get the same precision on a lower-mass star, they would be able to look at even lower-mass planets and so those really would be analogs of the Earth."

Currently, astronomers are working from locations such as the W.M. Keck Observatory in Hawaii and the French COROT mission. But the future holds several more observatories and telescopes that will continue our search. NASA’s Kepler observatory is scheduled for launch in February of next year, while the James Webb Space Telescope is set to launch and replace Hubble in 2013.

So the law of statistics, based on the recent discoveries of smaller and smaller planets, and the increase in discoveries, suggests that we’ll be seeing a twin-Earth any year now.

Posted by Josh Hill with Casey Kazan.